This invention relates generally to rinse tanks and particularly to a rinse tank for rinsing residue from fine apertures in a moving strip of material.
Many thin metal items, such as shadow masks for color picture tubes, are made by acid etching. In such etching a pattern of a part to be etched is photographically produced on a photoresist material which is coated onto the metal. The photoresist material is exposed to light through a transparent medium bearing the opaque pattern. The unexposed portion of the photoresist material is washed away leaving bare metal along the pattern, while the exposed material protects the metal from the acid. Typically, a large number of the patterns are photographically produced on a long strip of metal which is horizontally pulled through an acid etch tank. The acid in the etch tank etches through bare metal to produce the desired part. Frequently, the pattern is produced on both sides of the metal strip and the etching occurs on both sides.
The metal strip moves continuously through the etch tank. After etching is completed and the strip exits from the tank a large amount of acid clings to the photoresist material on both sides of the strip. It is essential that this acid be removed as soon as possible. Typically, the acid is removed by spraying the strip with a rinsing solution in a spray chamber. The rinsing solution typically is either clean water or an alkaline solution which neutralizes the acid. Also, after the metal strip is rinsed with the alkaline material it is further rinsed with fresh water to remove the alkaline rinse.
When the parts being etched are shadow masks for high resolution visual displays, the apertures in the shadow mask are very fine. Accordingly, the spraying of the rinsing fluid onto the shadow mask does not cause the rinsing fluid to fully enter the apertures and residue in the apertures, therefore, is not fully washed away. For this reason, there is a need for a rinse tank which forces the rinsing fluid into the fine apertures to more fully remove residue from the apertures.